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<head><meta charset="utf-8"><title>I-prioritize #74018 ICE when playing around with existential · t-compiler/wg-prioritization/alerts · Zulip Chat Archive</title></head>
<h2>Stream: <a href="https://rust-lang.github.io/zulip_archive/stream/245100-t-compiler/wg-prioritization/alerts/index.html">t-compiler/wg-prioritization/alerts</a></h2>
<h3>Topic: <a href="https://rust-lang.github.io/zulip_archive/stream/245100-t-compiler/wg-prioritization/alerts/topic/I-prioritize.20.2374018.20ICE.20when.20playing.20around.20with.20existential.html">I-prioritize #74018 ICE when playing around with existential</a></h3>

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<a name="202839706"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/245100-t-compiler/wg-prioritization/alerts/topic/I-prioritize%20%2374018%20ICE%20when%20playing%20around%20with%20existential/near/202839706" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> triagebot <a href="https://rust-lang.github.io/zulip_archive/stream/245100-t-compiler/wg-prioritization/alerts/topic/I-prioritize.20.2374018.20ICE.20when.20playing.20around.20with.20existential.html#202839706">(Jul 03 2020 at 22:13)</a>:</h4>
<p><span class="user-group-mention" data-user-group-id="3111">@WG-prioritization/alerts</span> issue <a href="https://github.com/rust-lang/rust/issues/74018">#74018</a> has been requested for prioritization.</p>
<h1><a href="https://hackmd.io/WJ0G17DHTHGgv0OW9I2PxA?view#Unprioritized-I-prioritize">Procedure</a></h1>
<ul>
<li>Priority?</li>
<li>Regression?</li>
<li>Notify people/groups?</li>
<li>Needs <code>I-nominated</code>?</li>
</ul>



<a name="202839925"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/245100-t-compiler/wg-prioritization/alerts/topic/I-prioritize%20%2374018%20ICE%20when%20playing%20around%20with%20existential/near/202839925" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Léo Lanteri Thauvin <a href="https://rust-lang.github.io/zulip_archive/stream/245100-t-compiler/wg-prioritization/alerts/topic/I-prioritize.20.2374018.20ICE.20when.20playing.20around.20with.20existential.html#202839925">(Jul 03 2020 at 22:18)</a>:</h4>
<blockquote>
<p>The following (totally incorrect, nightly features dependent) code is rejected without an ICE on the mentioned beta version, but nightly handles this less gracefully.</p>
</blockquote>
<p>I think that makes it a <code>P-medium</code>?</p>



<a name="202864145"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/245100-t-compiler/wg-prioritization/alerts/topic/I-prioritize%20%2374018%20ICE%20when%20playing%20around%20with%20existential/near/202864145" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> lcnr <a href="https://rust-lang.github.io/zulip_archive/stream/245100-t-compiler/wg-prioritization/alerts/topic/I-prioritize.20.2374018.20ICE.20when.20playing.20around.20with.20existential.html#202864145">(Jul 04 2020 at 08:42)</a>:</h4>
<p>I think this can be <code>P-low</code>, considering that the compiler first outputs</p>
<div class="codehilite"><pre><span></span><code>   Compiling playground v0.0.1 (/playground)
error[E0658]: trait aliases are experimental
 --&gt; src/lib.rs:2:1
  |
2 | trait UsedAlias&lt;&#39;a, T&gt; = Iterator&lt;Item = &amp;&#39;a UsedTypeAlias&lt;T&gt;&gt;;
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #41517 &lt;https://github.com/rust-lang/rust/issues/41517&gt; for more information
  = help: add `#![feature(trait_alias)]` to the crate attributes to enable

error[E0658]: trait aliases are experimental
 --&gt; src/lib.rs:4:1
  |
4 | trait OtherTraitAlias&lt;T&gt; = where for&lt;&#39;r&gt; &amp;&#39;r Self: IntoIterator&lt;Item = UsedTypeAlias&lt;T&gt;&gt;;
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #41517 &lt;https://github.com/rust-lang/rust/issues/41517&gt; for more information
  = help: add `#![feature(trait_alias)]` to the crate attributes to enable

error[E0658]: `impl Trait` in type aliases is unstable
  --&gt; src/lib.rs:11:28
   |
11 |     type Associated = S&lt;T, impl UsedAlias&lt;&#39;a, T&gt;&gt;; // Line also necessary for the ICE
   |                            ^^^^^^^^^^^^^^^^^^^^^
   |
   = note: see issue #63063 &lt;https://github.com/rust-lang/rust/issues/63063&gt; for more information
   = help: add `#![feature(type_alias_impl_trait)]` to the crate attributes to enable
</code></pre></div>



<a name="202864208"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/245100-t-compiler/wg-prioritization/alerts/topic/I-prioritize%20%2374018%20ICE%20when%20playing%20around%20with%20existential/near/202864208" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> lcnr <a href="https://rust-lang.github.io/zulip_archive/stream/245100-t-compiler/wg-prioritization/alerts/topic/I-prioritize.20.2374018.20ICE.20when.20playing.20around.20with.20existential.html#202864208">(Jul 04 2020 at 08:44)</a>:</h4>
<p><a href="https://github.com/rust-lang/rust/issues/69239">https://github.com/rust-lang/rust/issues/69239</a> is the same with <code>#![feature(const_generics)]</code> and is <code>P-medium</code>, so either is fine for me <span aria-label="shrug" class="emoji emoji-1f937" role="img" title="shrug">:shrug:</span></p>



<a name="203005329"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/245100-t-compiler/wg-prioritization/alerts/topic/I-prioritize%20%2374018%20ICE%20when%20playing%20around%20with%20existential/near/203005329" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Léo Lanteri Thauvin <a href="https://rust-lang.github.io/zulip_archive/stream/245100-t-compiler/wg-prioritization/alerts/topic/I-prioritize.20.2374018.20ICE.20when.20playing.20around.20with.20existential.html#203005329">(Jul 06 2020 at 15:43)</a>:</h4>
<p>I think this issue will need to be fixed for <code>#![feature(type_alias_impl_trait)]</code> to be stabilized, so I would rather see <code>P-medium</code> than <code>P-low</code>, what do you think?</p>



<a name="203115599"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/245100-t-compiler/wg-prioritization/alerts/topic/I-prioritize%20%2374018%20ICE%20when%20playing%20around%20with%20existential/near/203115599" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> triagebot <a href="https://rust-lang.github.io/zulip_archive/stream/245100-t-compiler/wg-prioritization/alerts/topic/I-prioritize.20.2374018.20ICE.20when.20playing.20around.20with.20existential.html#203115599">(Jul 07 2020 at 15:13)</a>:</h4>
<p>Issue <a href="https://github.com/rust-lang/rust/issues/74018">#74018</a>'s prioritization request has been removed.</p>



<a name="203115791"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/245100-t-compiler/wg-prioritization/alerts/topic/I-prioritize%20%2374018%20ICE%20when%20playing%20around%20with%20existential/near/203115791" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> DPC <a href="https://rust-lang.github.io/zulip_archive/stream/245100-t-compiler/wg-prioritization/alerts/topic/I-prioritize.20.2374018.20ICE.20when.20playing.20around.20with.20existential.html#203115791">(Jul 07 2020 at 15:14)</a>:</h4>
<p>went with p-medium</p>



<hr><p>Last updated: Aug 07 2021 at 22:04 UTC</p>
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